1. Field of the Invention
This invention relates generally to methods and apparatus for covering the output orifice of an irrigation sprinkler, and more specifically to a flush cap which also facilitates flushing the sprinkler during installation.
2. Description of the Prior Art
Underground sprinkler systems include a source of water, and a labyrinth of pipes which convey that water to sprinklers which extend above ground to distribute the water for irrigation. These sprinklers are commonly of the type which include a riser that is biased to a normal position below the surface of the ground, but which is adapted to resist the bias and rise to an elevated position above the ground when activated by water pressure. This riser has an output channel and an output orifice which is adapted to receive a nozzle at the end of the riser.
When underground sprinkler systems are installed, small trenches are dug to receive the pipes and sprinklers. After these elements are assembled, the trenches are back filled to bury the pipe and a major portion of each sprinkle. During this installation procedure, the sprinklers are susceptible to damage from rocks and other debris. For this reason, the sprinkler nozzle, which is perhaps the most fragile part of the sprinkler, is not attached until after the back fill process is completed. In the absence of the nozzle, if the output orifice were left open, the backfilled dirt and debris would enter the sprinkler. To avoid this consequence, removable caps have been provided to cover the output orifice during the backfill operation.
Even with the protective covers, it has been found that dirt can enter the system at any point where pipes or sprinklers are connected during the assembly process. In order to clear the system of all such dirt and debris, it has been customary to flush the system with water prior to the installation of the nozzles. The covers have been removed during this process in order to open the output orifice. When the flushing process is completed, sometimes the dirt re-enters the orifice from the surrounding flush pool thereby contaminating the system before the nozzles can be installed.
Special covers in the form of flush caps have been used in order to facilitate the flush operation without removing the cover. These flush caps have commonly been screwed into the nozzle threads at the output orifice. In many cases the screw threads have not provided a sufficiently positive lock to withstand the water pressures. In other cases, the threaded flush caps have been difficult to remove against the bias of the sprinkler riser.